This invention relates generally to valves for controlling fluid flow and, more particularly, to shear seal valves for controlling the flow of pressurized hydraulic fluid.
Shear seal valves are typically used in fluid pressure systems to control fluid flow and commonly include a valve body having a central chamber housing a reciprocable slide. Generally, the slide is axially movable between different positions within the valve body so as to control fluid flow through passages formed in both the valve body and the slide itself. Fluid leakage is prevented by means of tubular shear seals which are housed in ports formed in either the valve body or the slide. Such shear seals include flat, sealing, end faces which slideably engage either the slide or the valve body as the valve is operated. Various known shear seals rely on the force developed by the pressurized hydraulic fluid itself to help bias the shear seal tightly against the adjacent valve body or slide so as to assure a tight seal and thereby avoid fluid leakage.
The fluid pressure forces forcing the shear seals against the opposed flat faces of the valve body or slide can restrict relative movement between the valve body and slide and thereby increase the actuating force necessary to operate the valve. This is particularly true in high pressure hydraulic systems where fluid pressures as high as 10,000 lbs. per square inch (psi) can be encountered. Low slide forces are necessary where valves are actuated automatically by electrically operated solenoids, and use of electrically actuated valves has increased significantly because of computer controlled or remote controlled manufacturing operations. Prior shear seal valve designs have, therefore, sought to minimize sliding friction between the slide and the valve body while simultaneously allowing substantial contact forces to be developed between the shear seals and the slide or valve body so as to minimize fluid leakage. Typically, this has been achieved by utilizing some sort of bearing arrangement to support the slide in the shear seal valve housing.
One example of a prior bearing arrangement for supporting a slide in a shear seal valve is shown in U.S. Pat. No. 3,761,054 to Abdo which issued Sept. 25, 1973. As therein illustrated, a slide is supported by means of four disk-shaped bearing assemblies mounted to the ends of a pair of axles extending through each end of the slide. Although effective in reducing friction, the mounting of the bearings to the slide increased the length of the slide as well as the overall size of the resulting shear seal valve.
In view of the foregoing, it is a general object of the present invention to provide a new and improved shear seal valve.
It is a more specific object of the present invention to provide a new and improved shear seal valve that is suitable for use in high pressure hydraulic systems and which can be reliably actuated through use of relatively small actuating forces.
It is a still more specific object of the present invention to provide a new and improved shear seal valve that is compact and easily manufactured.